Rotor for a motor, and a motor and an appliance comprising the rotor, and a method for making a rotor

ABSTRACT

A rotor for a motor comprising a frame having a hub for connecting the rotor to a shaft and a perimeter portion for interacting with a stator of the motor to cause the rotor to rotate about an axis of rotation. The frame comprises legs extending from an outer portion of the frame towards the hub, each leg having an inner end at the hub and an outer end at the outer portion of the frame, the inner ends of a first plurality of legs being spaced from the inner ends of a second plurality of legs in a direction along the axis of rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 15/087,741,filed Mar. 31, 2016, which is a continuation of U.S. patent applicationSer. No. 13/805,984, filed Dec. 20, 2012, which is a national phase ofInternational Application No. PCT/NZ2011/000121, filed Jun. 27, 2011,which claims priority from U.S. Patent Provisional Application No.61/358,746, filed Jun. 25, 2010 and U.S. Provisional Application No.61/376,335, filed Aug. 24, 2010.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to electric motors, and particularlymotors of a type that are used as the main drive motor for a domesticlaundry.

Description of the Related Art

EP 1548171 describes a drive system for washing machines. The drivesystem comprises a motor with a large diameter shallow stator and arotor with magnets external to the stator. The stator is supported onthe end of a washing tub as shown in FIG. 2 of that application. Thestator has an aperture for a drive shaft to pass through. As shown inFIGS. 2 and 16 of EP patent application 1548171, a rotor, which is to befixed to the drive shaft for driving the rotating drum of a washingmachine, has a ring of permanent magnet material supported on the insideof a steel backing ring. A frame extends between the hub of the rotor(through which the shaft can extend) and the steel backing ring. Thebacking ring and frame may be formed together. The permanent magnetmaterial is made of a set of curved permanent magnet elements. Thepermanent magnet material is magnetised after physical construction ofthe rotor. A typical rotor has more than 30 poles magnetised into thering of magnetic material. The polarity of the poles alternatesproceeding around the ring.

The rotor as shown in FIG. 16 of EP 1548171 includes cooling fins 42 anda radial embossing 43 at a predetermined position between adjacent fins.The fins are cut and bent from predetermined positions of a horizontalsurface of the rotor frame for blowing air during rotation of the rotor40, to cool and dehumidify the motor. Each embossing reinforces therotor frame 41. The embossings 43 can be formed by a pressing operation.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved rotor ora motor with such a rotor, or an appliance that uses such a motor orrotor, or to at least provide the industry with a useful choice.

In one aspect the present invention consists in a rotor for a motorcomprising a hub for connecting the rotor to a shaft, a perimeterportion for interacting with a stator of the motor to cause the rotor torotate about an axis of rotation, and a frame between the hub and theperimeter portion, wherein the frame comprises legs extending from thehub outwards towards the perimeter portion, each leg having an inner endat the hub, the inner ends of a first plurality of legs being axiallyspaced from the inner ends of a second plurality of legs.

Preferably the frame is metal and the first plurality of legs or thesecond plurality of legs or both are bent from the frame to axiallyspace the inner ends of the first plurality of legs from the inner endsof the second plurality of legs.

Preferably the hub comprises a reinforcing member for coupling the rotorto the shaft and over-moulded plastic material to couple the inner endof each leg to the reinforcing member.

Preferably the first plurality of legs and the second plurality of legsare interleaved, a leg from the first plurality of legs being adjacentto and between two legs from the second plurality of legs.

Preferably the frame comprises an annular outer portion between an outerend of the legs and the perimeter portion of the rotor, the legsextending between the hub and the annular outer portion.

Preferably the first plurality of legs and the second plurality of legsdiverge from the outer portion of the frame at a common axial positionof the outer portion of the frame.

Preferably the first plurality of legs have their inner end spaced toone side of the outer portion of the frame, and the second plurality oflegs have their inner end spaced to the other side of the outer portionof the frame.

Preferably the frame comprises a ring joining the inner ends of theplurality of first legs together or the inner ends of the plurality ofsecond legs together.

Preferably the hub comprises a reinforcing member coupled to the innerends of the legs for coupling the rotor to the shaft, the reinforcingmember comprising a shoulder on an outer circumference for seatingagainst a surface of the ring to position the reinforcing member axiallywith respect to the frame.

Preferably the hub comprises a reinforcing member coupled to the innerends of the legs for coupling the rotor to the shaft, and an outercircumference of the reinforcing member bears against an innercircumference of the ring to position the reinforcing member radiallywith respect to the frame.

Preferably each leg bent from the frame is bent at a fold line and theframe comprises an embossing at each fold line, the embossing bridgingbetween the outer portion of the frame and the leg.

Preferably the frame is formed from sheet metal, the legs being formedin one or more stamping, pressing or bending operations.

Preferably the frame is formed from steel.

Preferably the frame is formed from a single blank of sheet materialwith the plurality of first legs interleaved with the plurality ofsecond legs.

Preferably the frame comprises two parts, a first part having the firstplurality of legs and a second part having the second plurality of legs.

Preferably outer ends of the first plurality of legs and outer ends ofthe second plurality of legs are over-moulded together with plastic atthe rotor perimeter portion.

Preferably the first part comprises a ring joining the inner ends of theplurality of first legs together and the second part comprises a ringjoining the outer ends of the plurality of second legs together, or thefirst part comprises a ring joining the outer ends of the plurality offirst legs together and the second part comprises a ring joining theinner ends of the plurality of second legs together.

Preferably the legs are arranged radially about the hub.

Preferably the hub comprises a reinforcing member coupled to the innerends of the legs for coupling the rotor to the shaft and the reinforcingmember is formed of metal and contacts the frame.

Preferably an inner circumference of the hub has splines forrotationally coupling the rotor to a shaft comprising correspondingsplines.

Preferably the rotor is an outside rotor for surrounding an insidestator, the rotor having a cylindrical side wall extending axially fromthe frame for mounting rotor elements for interacting with the stator tocause the rotor to rotate about the axis of rotation.

Preferably the cylindrical side wall is metal and is integrally formedwith the frame.

Preferably the cylindrical side wall is plastic over moulded to aperimeter of the frame.

Preferably the frame and hub are integrally formed of plastic.

Preferably the frame and the cylindrical side wall are integrally formedof plastic.

Preferably the hub, frame and cylindrical side wall are integrallyformed of plastic.

Preferably the second plurality of legs are in plane with the outerportion of the frame, the first plurality of legs formed to have theirinner ends spaced axially toward a corresponding stator side of therotor.

Preferably the hub comprises a reinforcing member for coupling the rotorto the shaft and overmoulded plastic to couple the reinforcing member tothe frame.

Preferably the rotor is for a brushless DC motor and the cylindricalside wall of plastic encapsulates a backing ring and magnets located atan inside of the backing ring.

Preferably the frame comprises a member radially spaced from the hub andlocated in between the inner ends and the outer ends of the first andsecond plurality of legs, the member extending circumferentially aroundthe hub, the member connecting between the first plurality of legs andthe second plurality of legs at a radial position intermediate betweenthe inner ends of the legs and the outer ends of the legs.

In another aspect the present invention consists in a motor comprising astator and a rotor as described above.

In another aspect the present invention consists in a laundry machinecomprising a tub, a drum rotationally mounted inside the tub, a driveshaft, and a motor for driving rotation of the drum via the shaftcomprising a stator fixed relative to the tub and a rotor coupled to theshaft, the rotor as described above.

In another aspect the present invention consists in a method ofmanufacturing a rotor comprising a hub for connecting the rotor to ashaft, a perimeter portion for interacting with a stator of the motor tocause the rotor to rotate about an axis of rotation, and a frame betweenthe hub and the perimeter portion, the method comprising the steps of:i) stamping the frame from a sheet of metal to form legs, each legextending outwardly from an inner end to be attached to the hub towardsthe perimeter portion, ii) bending a first plurality of legs or a secondplurality of legs or both from the frame so that the inner ends of thefirst plurality of legs are axially spaced from the inner ends of thesecond plurality of legs, iii) attaching the hub to the inner ends ofthe legs.

Preferably step ii) comprises the steps of: ii)a) placing the inner endsof the legs in a mould cavity, ii)b) injecting plastic into the cavityto overmould the inner ends of the legs together at the hub, ii)c)releasing the frame from the mould, the hub being formed at least fromthe plastic.

Preferably step iii) comprises the steps of: iii)a) placing the innerends of the legs and a reinforcing member for coupling the rotor to theshaft into a mould cavity, iii)b) injecting plastic into the cavity toovermould the inner ends of the legs and the reinforcing member togetherat the hub, iii)c) releasing the frame and the reinforcing member fromthe mould, the reinforcing member and plastic forming the hub.

The term “comprising” as used in this specification and claims means“consisting at least in part of”. When interpreting each statement inthis specification and claims that includes the term “comprising”,features other than that or those prefaced by the term may also bepresent. Related terms such as “comprise” and “comprises” are to beinterpreted in the same manner.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described by way ofexample only and with reference to the drawings.

FIG. 1 shows a rotor according to one embodiment of the presentinvention.

FIG. 2 shows a stator that may be used together with the rotor of FIG. 1to form a motor according to one embodiment of the present invention.

FIG. 3 is a cross sectional view of the rotor of FIG. 1.

FIG. 4 is a cross sectional view of the rotor of FIG. 1 and a stator,the rotor and stator forming a motor according to one embodiment of thepresent invention.

FIG. 5 is an exploded view of the rotor of FIG. 1.

FIGS. 6A to 6C are part views of rotors according to alternativeembodiments of the present invention, and FIGS. 6D and 6E show rotorsaccording to further alternative embodiments of the present invention.

FIGS. 7A to 7C are views of a frame for the rotor of FIG. 1, FIG. 7Abeing an end view, FIG. 7B being a cross sectional view through a centreof the frame, and FIG. 7C being a perspective view.

FIG. 8 shows an alternative frame for a rotor according to anotherembodiment of the present invention.

FIG. 9 shows a rotor according to another embodiment of the presentinvention.

FIG. 10 is a cross sectional view of the rotor of FIG. 9.

FIG. 11 shows a diagrammatic cutaway view of a washing machine of avertical axis type that may incorporate a rotor and/or motor accordingto the present invention.

FIG. 12 shows a diagrammatic view of a horizontal axis washing machinewith front access that may incorporate the rotor and/or motor accordingto the present invention.

FIG. 13 shows a diagrammatic view of a horizontal axis washing machinewith top or tilt access that may incorporate the rotor and/or motoraccording to the present invention.

FIG. 14 shows a diagrammatic view of a horizontal axis laundry machinewith tilt access that may incorporate the rotor and/or motor accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In one embodiment of the invention, a rotor 1 is provided as shown inFIG. 1. The rotor 1 is used in a motor together with a stator 10 asknown in the art. An example of a typical stator 100 is shown in FIG. 2.

The rotor of one embodiment of a rotor according to the presentinvention is described with reference to FIGS. 1, 3 and 5. The rotorcomprises a cylindrical side wall 10 and an end wall or frame 3.Permanent magnets 5 are located at a perimeter of the frame. Preferablythe magnets 5 are located at an inner circumference of the side wall tobe positioned outside the poles of the stator when the rotor is in usein a motor. Preferably the magnets are located at an innercircumferential surface of the rotor side wall.

The frame 3 spans between the rotor cylindrical side wall 10 and a hub9. The hub provides a means to mount the rotor to a shaft for driving adriven component of a machine, for example the laundry drum in a laundrymachine. In use the rotor rotates relative to the stator about an axisof rotation 20.

The hub 9 connects the rotor 1 to a drive shaft. The frame comprises aplurality of legs 11 extending from an outer portion 12 of the frame 3towards the hub 9. Each leg has an inner end 13 at the hub and an outerend 14 at the outer portion of the frame. The legs are arranged at thehub so that the inner ends of a first plurality of legs 11 a are spacedfrom the inner ends of a second plurality of legs 11 b in a directionalong the axis of rotation 20. The inner ends of the legs are fixed tothe hub.

The legs provide a rigid connection between the hub and the frame, andprovide rigidity to the frame to prevent or resist bending or flexing ofthe frame. Spacing the inner ends of the legs axially apart at the hubprovides rigidity to the frame to prevent or resist bending or flexingof the frame, compared to a frame where an inner portion of the frame isattached to the hub at a single axial position only, for example asshown in FIG. 1 of U.S. Pat. No. 6,474,114. A rigid frame is desirableto ensure the elements of the rotor that magnetically interact withpoles of the stator are positioned accurately relative to the stator.

The illustrated embodiment has the inner ends of the first plurality oflegs spaced to one side of the outer portion of the frame, and the innerends of the second plurality of legs spaced to the other side of theouter portion of the frame. This allows the hub 9 to be positionedapproximately in plane with the outer portion 12 of the frame if this isdesired for a particular motor arrangement. Alternatively, it may bedesirable to position the hub towards an outer side of a motor assembly,in which case the first plurality of legs 11 a could be arranged inplane with the outer portion 12 of the frame, and the second pluralityof legs 11 b formed to have their inner ends spaced axially away from acorresponding stator. Alternatively, it may be desirable to position thehub towards an inner side of a motor assembly, in which case the secondplurality of legs 11 b could be arranged in plane with the outer portion12 of the frame, and the first plurality of legs 11 a formed to havetheir inner ends spaced axially toward a corresponding stator.

The inner ends 13 of the legs are preferably rigidly fixed to the hub.The legs could be welded, fixed with fasteners, bonded or otherwisefixed to the hub. In the preferred embodiment the legs are over-mouldedin a plastic portion of the hub 9. Preferably the hub 9 comprises areinforcing member 2 for coupling the rotor to a shaft and over-mouldedplastic material 7 to couple the inner end of each leg to thereinforcing member. For example, as shown the reinforcing member 2comprises splines 8 at an inner circumference of the reinforcing memberfor rotationally coupling the rotor to a shaft comprising correspondingmating splines. Alternatively the reinforcing member may be keyed to theshaft or otherwise rotationally coupled to the shaft.

Alternatively, the hub 9 may comprise a plastic material over-moulded tothe inner ends of the legs, an inner circumference of the plastic hubformed to mate with a shaft, as illustrated in the part view of FIG. 6A.Splines or other feature such as a key way 25 formed in the innercircumference of the plastic hub 9 provide for rotational coupling ofthe hub to a shaft.

The inner ends of the legs may include features that assist withsecuring the inner ends of the legs to the plastic hub 9. For example,as shown in FIG. 6B, the ends of the legs may include a portion 26 thatextends in an axial direction or at some angle to a plane perpendicularto the axis of rotation. The inner ends of the legs may be shaped toassist with securing the inner ends of the legs to the plastic hub, forexample, as best shown in FIG. 7A, the inner ends of the legs includeshoulders 28 facing radially outwards. Shoulder 28 on each side of eachleg is formed by providing a gap 27 between adjacent legs, for exampleby removing a sliver of material from between adjacent legs except atthe innermost portion of each leg.

In an alternative embodiment as shown in FIG. 6C, the inner ends of thelegs may be welded to a hub 9.

As shown in FIGS. 1 and 3 to 5, the first plurality of legs 11 a and thesecond plurality of legs 11 b diverge from the outer portion 12 of theframe, to achieve an axial distance between the inner ends of the firstplurality of legs and the second plurality of legs at the hub 9. In theillustrated embodiment, the outer end 14 of the legs 11 a, 11 b arelocated at the outer portion of the frame 12 at a common axial positionof the outer portion of the frame 3. The legs diverge from the outerportion of the frame from a common axial position at the outer portionof the frame 3.

Preferably the frame 3 is formed from sheet metal and the firstplurality of legs or the second plurality of legs or both are bent fromthe frame to space the inner ends of the first plurality of legs fromthe inner ends of the second plurality of legs in a direction along theaxis of rotation. Preferably the frame 3 is formed from sheet metal, forexample a sheet of steel, the legs 11 being formed in one or morestamping, pressing or bending operations. In the preferred embodimenteach leg bent from the frame is bent at a fold line 15 and the frameincludes an embossing 16 at each fold line, the embossing bridgingbetween the outer portion 12 of the frame and the leg 11. The embossingat each bent leg provides rigidity to the leg in an axial direction toassist in maintaining the position of the leg at least during themanufacture of the rotor prior to fixing the inner end of the legs tothe hub of the frame. Preferably the embossing 16 is pressed into themetal frame in the same axial direction as the axial direction the legis bent towards from the outer portion of the frame.

As best shown in FIG. 3, the inner ends of the legs are preferablyaligned perpendicular to the axis of rotation for attaching to the hub.Where the frame is formed from sheet metal, the inner ends of the legsare folded at a fold line 23 to be perpendicular or at some other angleto the axis of rotation. The frame may comprise an embossing (not shown)at each fold line 23 at the inner end of each leg, to provide rigidityto the leg in an axial direction to assist in maintaining the positionof the inner end of the leg at least during the manufacture of the rotorprior to fixing the inner end of the legs to the hub of the frame.

Spacing the inner ends of the legs axially apart at the hub providesrigidity to the frame to prevent or resist bending or flexing of theframe. Any axial distance between the inner ends of a first plurality oflegs and a second plurality of legs attached to the hub providesincreased rigidity compared to a frame where an inner portion of theframe is attached to the hub at a single axial position only. However,the inner ends of the first plurality of legs are preferably spacedapart from the inner ends of the second plurality of legs by 10 mm to 50mm for a typical size of rotor required in a motor for driving arotatable drum in a laundry appliance. For example, a rotor according anembodiment of the present invention and suitable for use in a motor of alaundry appliance may have a hub with an outer diameter of approximately80 mm, a leg length of approximately 50 mm between the hub and the rotorouter portion 12, and an axial distance between the inner ends of thefirst plurality of legs and the second plurality of legs ofapproximately 16 mm. For a typical size of rotor required in a motor fordriving a rotatable drum in a laundry appliance, the first plurality oflegs and the second plurality of legs preferably diverge from the outerportion of the frame at an angle of approximately 5 degrees to 30degrees between the legs of the first and second plurality of legs. Atypical rotor required in a motor for driving a rotatable drum in alaundry appliance and incorporating the present invention may have anouter diameter of approximately 300 mm, a hub diameter of approximately80 mm, and a leg length spanning between the hub and the outer portionof the frame of approximately 50 mm, with the inner ends of the firstplurality of legs spaced axially from the inner ends of the secondplurality of legs by approximately 16 mm.

Preferably there are at least three legs in the first plurality of legsand three legs in the second plurality of legs. Preferably there arethree to twelve legs in the first plurality of legs and three to twelvelegs in the second plurality of legs. Preferably the number of legs inthe first plurality of legs is the same as the number of legs in thesecond plurality of legs. Preferably the first plurality of legs and thesecond plurality of legs are interleaved, a leg from the first pluralityof legs being adjacent to and between two legs from the second pluralityof legs.

A shown in the accompanying Figures, the legs 11 are preferably wider atthe outer end 14 and narrower at the inner end 13. The legs 11 are widerat the outer end 14 and narrower at the inner end 13 to utilise themajority of the base material provided for manufacture of the frame, toprovide maximum rigidity. However, in an alternative embodiment, thewidth of the legs may be constant along the length of the legs, thewidth being determined by a maximum allowable width at the inner end ofthe legs. Preferably each leg is symmetrical about a radial centre line.Preferably each leg is wedge shaped, the outer end of each leg beingwider than the inner end of the leg. Preferably the legs 11 are arrangedradially about the hub.

The frame 3 may comprise a ring 17 joining either the inner ends of theplurality of first legs together or the inner ends of the plurality ofsecond legs together. The ring 17 strengthens the frame and the strengthof the connection between the hub and the frame compared to a framewithout such a ring.

As discussed above, one embodiment of a rotor according to the presentinvention comprises a hub 9 having a reinforcing member 2 over-mouldedto the frame 3. The ring 17 can be used to assist with placement of thereinforcing member 2 relative to the frame 3 during manufacture. Forexample, the reinforcing member 2 may comprise a shoulder 18 on an outercircumference for seating against an axially facing surface 19 of thering to position the reinforcing member axially with respect to theframe. The reinforcing member is positioned relative to the frame priorto permanently fixing the reinforcing member to the frame. Furthermorean outer circumference of the reinforcing member may bear against aninner circumference of the ring to position the reinforcing memberradially with respect to the frame. Alternatively, where the frame doesnot include such a ring, the inner end of the legs are preferablydimensioned to contact the reinforcing member to position thereinforcing member relative to the frame prior to permanent fixing ofthe reinforcing member to the frame. The leg length and outer diameterof the reinforcing member may be chosen so that the outer circumferenceof the reinforcing member bears against a radially inner facing surfaceof at least three legs to radially position the reinforcing member 2relative to the frame 3. The reinforcing member may include an axiallyfacing shoulder on an outer circumference for seating against an axiallyfacing surface of the inner ends of the legs to position the reinforcingmember axially with respect to the frame.

Preferably the reinforcing member 2 contacts the frame 3 to assist withpositioning the reinforcing member relative to the frame. Preferably thereinforcing member is formed of metal. Preferably the frame is formed ofsteel. Preferably the reinforcing member is formed of steel.

An alternative frame 3′ for a rotor according to an alternativeembodiment of the present invention is illustrated in FIG. 8. To assistwith an understanding of this alternative frame, edges of the frame areshown as continuous lines and folds in the frame are shown as dashedlines. The frame 3′ is formed in two parts, 30 and 31. The first part 30has a first plurality of legs 11 a and the second part 31 has a secondplurality of legs 11 b. As shown, the first part has a ring 17 joiningthe inner ends 13 of the plurality of first legs together and the secondpart comprises a ring 29 joining the outer ends 14 of the plurality ofsecond legs together. The first and second parts are formed togetherinto the rotor at the hub and perimeter portion of the rotor. Forexample, the inner ends 13 of the first plurality of legs and the innerends of the second plurality of legs are over moulded together at thehub with plastic, the plastic over-mould forming at least a portion ofthe hub, and outer ends of the first plurality of legs and outer ends ofthe second plurality of legs are over-moulded together with plastic atthe rotor perimeter portion. In this embodiment, the outer ends 14 ofthe first plurality of legs can be spaced from the outer ends 14 of thesecond plurality of legs in a direction along the axis of rotation.Alternatively, the outer ends 14 of the first plurality of legs and theouter ends 14 of the second plurality of legs can diverge from a commonaxial position.

The rotor of the present invention may be used in any type of motorcomprising a rotor with a perimeter portion that interacts with a statorof the motor to cause the rotor to rotate relative to the stator aboutan axis of rotation. For example, a rotor according to the presentinvention may be used in a motor having an inner rotor and an outerstator, for example as illustrated in FIG. 2A of U.S. Pat. No.4,998,052. Alternatively, a rotor according to the present invention maybe used in a motor having a rotor outside the stator, for example abrushless DC motor as described in relation to FIG. 2 of US2007/0132323, or an induction motor as described in relation to FIG. 8of US 2007/0132323. Alternatively, a rotor according to the presentinvention may be used in a motor wherein elements of the rotor thatmagnetically interact with the stator are located on an axial side ofthe rotor frame 3 as illustrated in FIG. 6D, corresponding elements ofthe stator for magnetically interacting with the rotor elements beingarranged beside the rotor in an axial direction.

One illustrated embodiment of the present invention shows a rotor for amotor having an outside rotor surrounding an inside stator, the rotorhaving a cylindrical side wall extending axially from the frame formounting rotor elements for interacting with the stator to cause therotor to rotate about the axis of rotation. The cylindrical side wall 10is formed from plastic and is over moulded to a perimeter of the frame.In an alternative embodiment, the cylindrical side wall could be metalintegrally formed with the frame as illustrated in FIG. 6E. For example,the rotor frame and side wall could be pressed from a parent sheetmetal.

A rotor according to an alternative embodiment of the present inventionis shown in FIGS. 9 and 10. In this embodiment, the rotor comprises aplastic frame extending from the hub of the rotor to the perimeter ofthe rotor. The frame includes a plurality of legs 11 extending betweenan outer portion 12 of the frame 3 and the hub 9. The legs are arrangedat the hub so that the inner ends of a first plurality of legs arespaced from the inner ends of a second plurality of legs 11 b in adirection along the axis of rotation 20, in a similar structure to thatof the other embodiments of the present invention described withreference to FIGS. 1 to 8. In the embodiment of FIGS. 9 and 10, thesecond plurality of legs 11 b are arranged in plane with the outerportion 12 of the frame, and the first plurality of legs 11 a formed tohave their inner ends spaced axially toward a corresponding stator sideof the rotor. However, in an alternative rotor, the inner ends of thefirst plurality of legs may be spaced to one side of the outer portionof the frame and the inner ends of the second plurality of legs may bespaced to the other side of the outer portion of the frame or otherwise,as required by the geometry of a motor. The present invention requiresthe inner ends of the first plurality of legs to be spaced axially fromthe inner ends of the second plurality of legs. The axial position ofthe legs 11 relative to the outer portion or perimeter of the frame isdependent on the particular geometry of the rotor desired for aparticular motor assembly.

Preferably the hub 9 and the frame are integrally formed in plastic.Preferably the plastic circumferential side wall of the rotor and theplastic frame are integrally formed in plastic. Preferably the rotorhub, frame and outer circumferential wall are integrally formed inplastic together in a plastic injection moulding process.

The hub may comprise a reinforcing member 2 and plastic, the plastic ofthe hub overmoulded together with the rotor frame to the reinforcingmember 2.

Preferably the rotor frame includes a member 40 radially spaced from thehub in between the inner ends and the outer ends of the first and secondplurality of legs and extending circumferentially around the hub. Themember connects between the first plurality of legs and the secondplurality of legs at a radial position intermediate between the innerends of the legs and the outer ends of the legs. The circumferentialmember 40 provides rigidity to the structure of the rotor frame, andassists to prevent or resist bending of the legs 11 a and 11 b.

Preferably a rib 41 a, 41 b is provided at each leg 11 a, 11 b toincrease the structural rigidity of the frame. Preferably ribs 41 a and41 b extend in the radial direction of the rotor. As shown in FIGS. 9and 10, preferably each leg 11 a of the first plurality of legs has arib 41 a on a side of each leg 11 a that faces towards the secondplurality of legs 11 b. Preferably each leg 11 b of the second pluralityof legs has a rib 41 b on a side of each leg 11 b that faces towards thefirst plurality of legs 11 a. The rotor may include other ribs forstructural strength, for example, ribs 42 extending from the outer endof each leg of the first plurality of legs to the circumferential wall10 of the rotor.

The various rotor embodiments illustrated in the accompanying figuresare rotors for brushless DC motors. For the embodiments comprising aplastic cylindrical side wall, the cylindrical side wall 10 of plasticencapsulates a metal cylinder or backing ring 4 and magnets 5 located atan inside of the backing ring 4. The backing ring couples the magneticflux between the magnets and controls the inside radial dimension of theassembled magnets during manufacture. Preferably the backing ring isformed by winding or wrapping a strip of metal into a cylinder until adesired thickness is achieved. The magnets 5 are positioned at an innercircumferential surface of the backing ring and the backing ring andmagnets are moulded together by the plastic side wall preferably in aninjection moulding process. Preferably the inner surface of the magnetsis exposed at an inner circumferential surface of the cylindrical sidewall of plastic. For the embodiment of FIGS. 1 and 3 to 5, preferablythe backing ring, magnets and frame are moulded together by the plasticside wall preferably in an injection moulding process. For example, thebacking ring, magnets and frame may be placed within a mould cavity,plastic then being injected into the mould cavity to mould the frame,magnets and backing ring together. For the embodiment of FIGS. 9 and 10,the plastic side wall 10 is integrally formed in plastic with the frame3. Preferably the backing ring and magnets are placed within a mouldcavity, plastic then being injected into the mould cavity to mould themagnets and backing ring together with the moulded side wall 10 andframe 3. Where the hub includes a reinforcing member 2, preferably thereinforcing member, backing ring and magnets are placed within a mouldcavity, plastic then being injected into the mould cavity to mould themagnets and backing ring together with the side wall 10 and mould thereinforcing member into the hub, the frame being integrally formed withthe side wall and the hub in the same injection moulding process.

A rotor according to an embodiment of the present invention has legsextending from the hub outwards towards a perimeter of the rotor. Eachleg has an inner end at the hub. The inner ends of a first plurality oflegs are spaced axially from the inner ends of a second plurality oflegs. There are gaps 50 between the first plurality of legs and thesecond plurality of legs. This construction of rotor provides astructure that allows air pressure to equalise on each side of the rotorframe. As a rotor spins, the rotor can act as a fan, creating a pressuredifferential across the rotor frame. Prior art rotors include holes inthe rotor frame to alleviate a pressure difference across the rotorframe and to allow air to reach the stator to cool the stator windings.Holes added to the rotor can reduce rigidity of the rotor frame which isundesirable. A rotor according to the present invention does not requireholes to be provided in the rotor frame as the gaps between adjacentlegs of the rotor allows air flow across the rotor frame.

A rotor according to the present invention is rigid for a given amountof material used in the frame construction, as the position of the legsspace material away from a neutral axis of the rotor frame. Prior artframes may include ribs for rigidity, but such ribs must be large toprovide sufficient rigidity. A rotor with particularly deep ribs can actas a fan and cause a pressure difference across the rotor frame whichmay be undesirable.

An embodiment of the invention might comprise a washing machine with amotor comprising the rotor as described above, or another embodimentmight comprise the motor itself, or the rotor itself. For example, across section of a motor comprising a rotor described above is shown inFIG. 4. Alternatively, the rotor could be used in another application,such as a power generation apparatus.

A preferred method for manufacturing a rotor according to one embodimentof the present invention and comprising a hub for connecting the rotorto a shaft, a perimeter portion for interacting with a stator to causethe rotor to rotate about an axis of rotation, and a frame between thehub and the perimeter portion is listed below.

The preferred method comprises the steps of: i) stamping the frame froma sheet of metal to form legs, each leg extending outwardly from aninner end to be attached to the hub towards the perimeter portion, ii)bending a first plurality of legs or a second plurality of legs or bothfrom the frame so that the inner ends of the first plurality of legs areaxially spaced from the inner ends of the second plurality of legs, iii)attaching the hub to the inner ends of the legs.

Preferably step ii) comprises the steps of: ii)a) placing the inner endsof the legs in a mould cavity, ii)b) injecting plastic into the cavityto overmould the inner ends of the legs together at the hub, ii)c)releasing the frame from the mould, the hub being formed at least fromthe plastic.

Preferably step iii) comprises the steps of: iii)a) placing the innerends of the legs and a reinforcing member for coupling the rotor to theshaft into a mould cavity, iii)b) injecting plastic into the cavity toovermould the inner ends of the legs and the reinforcing member togetherat the hub, iii)c) releasing the frame and the reinforcing member fromthe mould, the reinforcing member and plastic forming the hub.

A laundry machine such as a dryer or a washing machine using the motordescribed could take one of many forms. For example, referring to FIG.11, one embodiment comprises a top loading washing machine with an outerwrapper and a tub suspended within the wrapper. A rotating drum withperforated walls is disposed in and rotatable within the suspended tubinside a cabinet. A motor, comprising a stator and rotor as previouslydescribed, is coupled to the rotating drum via a rotational shaft. Themotor can be operated by a controller to spin and oscillate the rotatingdrum to carry out washing of clothes.

Referring to FIG. 12, another embodiment comprises a front loadinghorizontal axis washing machine with an outer wrapper and a rotatingdrum housing suspended in the outer wrapper. A rotating drum is disposedin and rotatable within the rotating drum housing. A door providesaccess to the rotating drum for introducing or removing clothing to bewashed. A gasket provides a seal between the door and the rotating drum.A motor, comprising a stator and rotor as previously described, iscoupled to the rotating drum via a rotational shaft. The motor can beoperated by a controller to spin and oscillate the rotating drum tocarry out washing of clothes.

Referring to FIG. 13, another embodiment comprises a top loading or tiltaccess horizontal axis washing machine. The washing machine has an outerwrapper and a tub suspended within the outer wrapper. A rotating drumcan rotate within the tub. Clothes can be introduced and taken from therotating drum through an opening in the top of the drum. A motor,comprising a stator and rotor as previously described, is coupled to therotating drum via a rotational shaft. The motor can be operated by acontroller to spin and oscillate the rotating drum to carry out washingof clothes.

FIG. 14 shows a tilt loading horizontal axis washing machine. Thewashing machine has an outer wrapper and a tub suspended within theouter wrapper. A rotating drum can rotate within the tub. Clothes can beintroduced and taken from the rotating drum by tilting the drum. Amotor, comprising a stator and rotor as previously described, is coupledto the rotating drum via a rotational shaft. The motor can be operatedby a controller to spin and oscillate the rotating drum to carry outwashing of clothes.

It will be appreciated that FIGS. 11 to 14 show just four examples ofwashing machines that could utilise a motor with a rotor produced in themanner described above. Other embodiments of the present invention couldcomprise other drying or washing machines be envisaged by those skilledin the art, operated by a motor as described above.

What is claimed is:
 1. A rotor for a motor, comprising: a hub forconnecting the rotor to a shaft, a perimeter portion for interactingwith a motor stator to cause the rotor to rotate about an axis ofrotation, and a frame between the hub and the perimeter portion,wherein: the frame is stamped from a sheet of metal to form legs, eachleg extending outwardly towards the perimeter portion from an inner endattached to the hub, and a first plurality of legs or a second pluralityof legs or both are bent from the frame so that inner ends of the firstplurality of legs are axially spaced from inner ends of the secondplurality of legs.
 2. The rotor as claimed in claim 1, wherein the hubis formed at least in part from plastics material overmoulding the innerends of the legs together.
 3. The rotor as claimed in claim 1, furthercomprising a reinforcing member for coupling the rotor to the shaft,wherein the hub is formed from plastics material overmoulding the innerends of the legs and the reinforcing member together.
 4. The rotor asclaimed in claim 1, wherein the perimeter portion comprises acylindrical side wall at a perimeter of the frame, the cylindrical sidewall extending axially wherein the cylindrical side wall is formedeither: from plastics material overmoulded to the perimeter of theframe, or integrally with the frame from sheet metal.
 5. The rotor asclaimed in claim 4, wherein the rotor is a brushless DC motor rotor andthe cylindrical side wall is formed of plastics material whichencapsulates a backing ring and magnets located at an inside of thebacking ring.
 6. The rotor as claimed in claim 5, further comprising areinforcing member, for coupling the rotor to the shaft, the reinforcingmember having a shoulder on an outer circumference thereof and a surfaceof the inner ring seated against the shoulder to position thereinforcing member axially with respect to the frame.
 7. The rotor asclaimed in claim 5, further comprising a reinforcing member, forcoupling the rotor to the shaft, wherein an outer circumference of thereinforcing member bears against an inner circumference of the innerring to position the reinforcing member radially with respect to theframe.
 8. The rotor as claimed in claim 4, wherein the first pluralityof legs and the second plurality of legs are circumferentiallyinterleaved.
 9. The rotor as claimed in claim 4, wherein the framefurther comprises an inner ring joining the inner ends of the pluralityof first legs together or the inner ends of the plurality of second legstogether.
 10. The rotor as claimed in claim 1, wherein the frame furthercomprises an outer ring joining together outer ends of the first and/orsecond plurality of legs.
 11. A method of manufacturing a rotor having ahub for connecting the rotor to a shaft, a perimeter portion forinteracting with a motor stator to cause the rotor to rotate about anaxis of rotation, and a frame between the hub and the perimeter portion,the method comprising the steps of: stamping the frame from a sheet ofmetal to form legs, each leg extending outwardly towards the perimeterportion from an inner end, bending a first plurality of legs or a secondplurality of legs or both from the frame so that inner ends of the firstplurality of legs are axially spaced from inner ends of the secondplurality of legs, and attaching the hub to the inner ends of the legs.12. The method as claimed in claim 11, wherein the attaching stepcomprises: placing the inner ends of the legs in a mould cavity,injecting a plastics material into the cavity to overmould the innerends of the legs together at the hub, and releasing the frame from themould, the hub being formed at least from the plastics material.
 13. Themethod as claimed in claim 11, wherein the attaching step comprises:placing the inner ends of the legs and a reinforcing member for couplingthe rotor to the shaft into a mould cavity, injecting plastics materialinto the cavity to overmould the inner ends of the legs and thereinforcing member together at the hub, and releasing the frame and thereinforcing member from the mould, the reinforcing member and plasticsmaterial forming the hub.
 14. The method as claimed in claim 11, furthercomprising forming the perimeter portion as a cylindrical side wall at aperimeter of the frame, the cylindrical side wall extending axiallywherein either: the cylindrical side wall is formed from plasticsmaterial overmoulded to the perimeter of the frame, or the cylindricalside wall is formed integrally with the frame from sheet metal.
 15. Themethod as claimed in claim 14, wherein the cylindrical side wall isformed from plastics material and the rotor is a brushless DC motorrotor, the method further comprising locating magnets at an inside of abacking ring and encapsulating the backing ring in the cylindrical sidewall of plastics material.
 16. The method as claimed in claim 11,wherein the bending step further comprises circumferentiallyinterleaving the first plurality of legs and the second plurality oflegs.
 17. The method as claimed in claim 11, wherein the stamping stepincludes forming an inner ring joining the inner ends of the pluralityof first legs together or the inner ends of the plurality of second legstogether.
 18. The method as claimed in claim 17, further comprisingcoupling a reinforcing member, for coupling the rotor to the shaft, tothe inner ends of the legs, the reinforcing member having a shoulder onan outer circumference thereof and seating a surface of the inner ringagainst the shoulder to position the reinforcing member axially withrespect to the frame.
 19. The method as claimed in claim 17, furthercomprising coupling a reinforcing member, for coupling the rotor to theshaft, to the inner ends of the legs with an outer circumference of thereinforcing member bearing against an inner circumference of the innerring to position the reinforcing member radially with respect to theframe.
 20. The method as claimed in claim 11, wherein the stamping stepfurther comprises forming an outer ring joining together outer ends ofthe first and/or second plurality of legs.